[Measuring coronary circulation using an inert gas method--a comparison of common indicator gases]

Validation studies of inert gas techniques are limited in number and usually have not included circumstances with marked heterogeneity of flow. This study was intended to investigate the validity of the method in experimental animals under various hemodynamic conditions by parallel application of helium, argon, krypton and xenon as indicators and by comparison with direct flow measurements. Gases were applied by single breath inhalation. In order to avoid the limitations of conventional methods arising from the systemic recirculation of tracer and from shortened measuring periods we used continuous mass spectrometric recording and numeric deconvolution of the dilution curves in arterial and coronary venous blood. When the transit times are evaluated by "stochastic" analysis and commonly used tissue/blood partition-coefficients (lambda He = 0.95, lambda Ar = 1.1) the helium and argon values are found in reasonable agreement with reference flows. The effects of a shortening of measurements that are based on single integrated samples (Argon method) are shown under control conditions, adenosin infusion and elevated ventricular filling pressure. With xenon (lambda Xe = 0.7) coronary blood flow above 100 ml/min X 100 g is underestimated by the "stochastic" and by the "initial slope technique"; parallel measurements with argon suggest that in the initial slope technique a lambda Xe between 0.8 and 0.9 might be more adequate.